Single-dose pharmacokinetics of bupropion in adolescents: effects of smoking status and gender

Sustained-release (SR) bupropion (Zyban) is approved as a smoking cessation aid for adults. Since smoking often begins in adolescence, we determined the single-dose pharmacokinetics of bupropion SR in 75 adolescent subjects ranging from 13 to 18 years old. Subjects self-reported their smoking status. Urinary cotinine concentration was used to verify smoking status. Thirty-seven subjects (18 males, 19 females) were classified as cigarette smokers and 38 were nonsmokers (19 males, 19 females). Fasted subjects received one tablet (150 mg) of bupropion SR, and plasma samples were collected before (0) and 1/2, 1, 2, 3, 4, 6, 8, 24, 48, and 72 hours after dosing. Plasma samples were analyzed for bupropion and its three major metabolites (hydroxybupropion and the aminoalcohol isomers, erythrohydrobupropion plus threohydrobupropion, expressed as a composite) by solid-phase extraction, followed by LC/MS/MS. Factorial analysis of variance (ANOVA) was used to evaluate the effects of smoking and gender on pharmacokinetic parameters. Smokers and nonsmokers differed significantly (p < 0.05) in age and urinary cotinine (p < 0.01) concentration but did not differ significantly in mean weight, height, body surface area, or body mass index. The pharmacokinetic (PK) parameters for bupropion and hydroxybupropion did not differ between smokers and nonsmokers, but differences were found between male and female subjects. Mean values for area under the plasma concentration versus time curve (AUC0-->infinity), volume of distribution (Vd beta) normalized to body weight, maximum plasma concentration (Cmax), and elimination half-life (t1/2 beta) for bupropion were significantly (p < 0.05) greater in females than males, while clearance of bupropion normalized to body weight (CL/f) did not differ between males and females. Females also exhibited significantly (p < 0.05) larger values for hydroxybupropion mean AUC0-->infinity and Cmax than males. The mean ratio of hydroxybupropion to bupropion AUC for adolescents was approximately 4 to 5, which is lower than that previously reported for adults. In conclusion, smoking status does not affect the single-dose pharmacokinetics of bupropion SR in adolescents. However, females differ from males in several potentially important PK parameters for bupropion and its major metabolite, hydroxybupropion.
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